1. Field of the Invention
This invention relates to a cooling air duct and a cooling apparatus for cooling the inside of a housing principally of an electronic apparatus such as a computer or a communication apparatus.
2. Description of the Related Art
In recent years, as development of a computer in terms of the performance and the function proceeds, also the mounting density of printed circuit boards and parts provided in the inside of the computer increases and a rise of the internal temperature by heat generated by the parts increases. In order to cool a computer, a cooling system which employs a fan, that is, an air cooling system, is used principally. Where a fan is used, however, there is a limitation in cooling capacity, and also noise leaking from the inside to the outside of the apparatus makes a problem. Therefore, development of a cooling air duct and a cooling apparatus which have a reliable cooling performance while noise is suppressed is demanded.
Generally in an electronic apparatus such as a computer or a communication apparatus, an air cooling system is applied to cool the inside of a housing. In the air cooling system, principally a fan is used to suck external air into the housing to radiate heat of the inside of the housing. On the other hand, in a large computer or a like apparatus, a water cooling system wherein liquid is circulated in the inside of the apparatus to radiate heat is sometimes applied. However, for computers, an air cooling system which uses a fan is employed principally. It is to be noted that, in the air cooling system, the temperature is adjusted by the number of fans to be used. In particular, where a lower cooling temperature of the inside of the housing is desired, the number of fans to be used is increased.
FIGS. 12 and 13 show a construction of an ordinary computer to which an air cooling system is applied. FIG. 12 is a side elevational sectional view schematically showing an internal construction of the computer, and FIG. 13 is a view as viewed in the direction of an arrow mark XIII of FIG. 12.
Referring first to FIG. 12, a mother board 11, a floppy disk driver (FDD) 12, a CD-ROM (compact disk read only memory) 13, a hard disk apparatus 14, a power supply 15 and other components are provided in a housing 10 of the computer. A CPU (central processing unit) board 16 and various printed circuit boards 17 are mounted on the mother board 11.
In order to cool the inside of the housing 10 in which such various components as mentioned above are built, a plurality of (two in FIG. 12) fans 20 are provided at a front side (right side in FIG. 12) location in the housing 10. Further, a front panel 18 is provided on the front face side (right side of FIG. 12) of the housing 10. The front panel 18 has a plurality of ventilating slits 18a formed therein corresponding to the positions of the fans 20.
When the fans 20 operate, external air flows into the inside of the housing 10 through the ventilating slits 18a of the front panel 18 and cools the inside of the housing 10. The air warmed as a result of the cooling action is discharged to the outside of the housing 10 through a plurality of vent holes (not shown) formed in a rear panel 19 of the housing 10.
A cable 21 is connected to the computer.
In the cooling system described above, however, since the number of fans to be used is increased as a rise of the internal temperature of the computer increases, as the number of fans to be used increases, and also as the number of hard disk apparatus and other apparatus used in the computer increases, the problem of noise which leaks from the inside to the outside of the computer becomes more significant.
Particularly, in the computer shown in FIGS. 12 and 13, the structure for admitting external air into the inside of the housing 10 includes mere perforation of the ventilating slits 18a in the front panel 18, and the structure for discharging air in the housing 10 to the outside includes mere perforation of the vent holes in a metal plate (rear panel 19). Consequently, sound generated in the inside of the housing 10 leaks directly through the structures to the outside. Therefore, it is demanded to decrease noise with certainty.
As described above, with the air cooling system, while the number of fans to be used must be increased as a rise of the internal temperature of the apparatus (housing 10) increases, since the cooling capacity provided by the fans is limited, the internal temperature of the apparatus cannot be adjusted freely. Further, as the number of fans to be used increases, also noise leaking to the outside of the apparatus increases and makes a problem. On the other hand, the water cooling system can be adopted only by large computers and like apparatus and requires a high cost.
Therefore, it is demanded to make it possible to arbitrarily adjust the internal temperature of a housing of a computer or a like apparatus to assure a high cooling capacity without increasing the number of fans to be used while noise is decreased.